Reinforcement of precursor-derived Si–C–N ceramics with carbon nanotubes

Mechanical and electrical properties of polymer-derived Si–C–N ceramics reinforced by octadecylamine – Modified single-wall carbon nanotubes

“…Figure 5). The relevance of these three mechanisms is further supported by the homogenous distribution of the tubes in the matrix ( Figure 5), which may also explain the smaller fracture toughness of 1.8 MPa m 1/2 obtained for polymer-derived Si-C-N ceramics reinforced by 2 wt % of pristine SWCNTs [23]. It is furthermore noteworthy that the fracture toughness does not monotonously increase with rising SWCNT content, but rather displays a maximum of ~ 3.1 ± 0,2 MPa m 1/2 at 1 wt%, which is followed by a value of ~ 2.6 ± 0.2 MPa m 1/2 at the content of 2 wt%.…”

“…Especially the crack deflection mechanism should be operative in light of the high aspect ratio of the used SWCNTs, which represents a critical factor governing the efficacy of crack deflection along the interface [22,23]. Moreover, the tubes' high tensile strength and stiffness is expected to allow effective crack bridging ( Figure 7 b and c) and their pull-out (cf.…”

“…In a related work [22], MWCNTs were ultrasonically dispersed in a liquid polysilazane precursor polymer, with subsequent casting, pressure-less cross-linking and thermolysis at 1000°C. Preliminary investigations of the fracture toughness of thus obtained composites using a thermal loading method revealed that the extent to which the incorporated nanotubes enhance the mechanical properties depends strongly on their structural characteristics, in particular their aspect ratio [23]. Recently, we have utilized single-wall carbon nanotubes (SWCNTs) for the reinforcement of Si-C-N polymer-derived ceramics, and found that the increase of Young's modulus increases with the dispersion degree of the nanotubes inside the amorphous matrix [24].…”

“…However, while it is well-documented that the incorporation of SWCNTs into polymerderived amorphous ceramics can enhance their mechanical performance and electrical conductivity, detailed studies of the fracture toughness are very limited. Recent results reveal that the incorporation of MWCNT into Si-C-N amorphous ceramics and the formation of CNT -matrix interfaces lead to 25 % increase of the fracture toughness [23]. Due to their small diameter SWCNT´s basically provide a means to increase the interface area without changing carbon nanotubes weight fraction.…”

Ceramic matrix composites containing carbon nanotubes

“…The problem may be particularly acute in glass-ceramics where nucleation effects are likely to be important. Katsuda et al 129 reported large mechanical improvements in 10 vol% CNT/barium aluminosilicate glass- of 40% (60.51GPa) and 160% (2.74MPa.m 1/2 ), respectively for the 10vol% CNT system 92 . In contrast, borosilicate glass composites containing modified-MWNTs, produced using a sol-gel method, were sintered at lower temperatures without inducing 25 crystallisation (see Figure 7) 100 .…”